Modern digital type telephone exchanges, of the type suitable to switch vocal and/or data signals in the form of PCM signals (Pulse Code Modulation), are usually designed to include the presence of a plurality of input/output modules, to each of which a predetermined number of users and/or a predetermined number of trunk lines can be connected. Each of the modules includes a processing unit for analysing the signalling criteria associated to voice and/or data signals, and also to structure them in the form of messages which can be switched between the modules.
It is known, in modern digital switched exchanges, switching operations concerning vocal and/or digital signals are carried out by means of a connection network on the basis of indications contained in the signal messages.
The connection network includes switching modules which in turn also include a processing unit.
Switching operations of signal messages can be carried out by using predetermined channels of the connection network, or by means of a switching network that is separate from the connection network. However it must be kept in mind that use of the connection network for switching signal messages involves the introduction of time delays necessary for crossing the network which are fundamentally caused by the times required to carry out connection network pre-patterning operations. In some circumstances the crossing times, mentioned above, are not compatible with the times required for correct operation of the switched exchange.
The fact, must also be kept in mind, that realization of a signal message switching network that is separate from the connection network, makes it possible to avoid the above described inconveniency concerning the transit times of messages, but also involves overcoming certain technical problems such as the following:
(a) switching messages with a number of words (bytes) that differs from message to message;
(b) switching messages which are output from the single modules in a non cyclic manner and according to a rhythm (the number of messages in a time unit) which differs from module to module, thus avoiding the danger of losing messages;
(c) synchronize the output module and the destination module with each other;
(d) allow a generic message to be sent to a single destination module, as also to a group of modules or to all the modules;
(e) guarantee scanning of all modules in a predetermined time interval;
(f) carry out useful functions for diagnosis of the switched message network and of the organs linked up to it.
One purpose of the present invention is to realize a fast switching network of the signal messages, that is separated from the connection network, and has the aforementioned requisites.
Such a switching network has been described, for example, by Bovo et al in the article "UT 100/60--An electronic digitale family of exchanges for a large capacity Applications" Proceeding of ISS 1/84--Florence, Italy; Session 14 B, pages 5; page 5, left-hand) with particular reference to FIG. 5 et al.
FIG. 5 of the Bovo article shows a message distributor module block diagram where the message distributor network, connected to N external Module Processors, comprises (connected one another) N input interfaces R, multiplexing means driven by a control logic and N output interfaces R.
Therefore an object of the present invention is a network for switching messages between a plurality h of processing unity, comprising h input interface units; multiplexing means driven by scanning means, whose inputs are connected to the outputs of the input interface units, and h output interface units whose inputs are connected, in parallel one another, to the output of the multiplexing means.
The above network for carrying out an object of the invention includes the following:
each interface unit is designed to be connected to a channel output from its respective processing unit, to memorize a plurality of messages, to activate a first output after memorizing at least one message, to make an active signal available on a second output for the complete duration of a message excepting during its last byte, to output a message on a third output in reply to receiving an enabling signal;
the multiplexing means receive the first, second and third output of the said input interface units on their input, and to connect the same to their own first, second and third output on the basis of the address bits applied to their own monitoring inputs;
the scanning means, designed to forward the said address bits to the multiplexing means to stop, or begin scanning operations again, in reply to picking up the enabling of the first output, or alternatively in reply to picking up the disenabling of the second output, of the multiplexing means;
decoding means, receiving on their input said address bits, designed to provide the said input interface units with enabling signals;
h output interface units, each of which can be connected to an channel entering its respective processing unit, and receive the messages corresponding to the third output of the multiplexing means and also designed to memorize them if the indicator present in a predetermined byte of the message coincides with the indicator assigned to said units.
Further objects of the invention will be made clear by the description given henceforth which refers to a form of embodiment given purely as an example without intending to limit the scope of the invention in any way, and completed with the attached drawings in which: